The International Telecommunication Union Telecommunication Sector (ITU-T) and the Institute of Electrical and Electronic Engineers (IEEE) are promoting the standardization of optical transport network (OTN) technology. According to the OTN standards, different kinds of client signals are transmitted in a transparent manner in an optical network using wavelength division multiplexing technology.
Japanese Laid-open Patent Publication No. 2014-093558 discusses a related art.